Eggshell Quality in Laying Hens

D. R. Korver

University of AlbertaEdmonton, Alberta, Canada

Eggshell Formation• First phase

– First ~5 hours of calcification

• Ca crystals begin to form

• Second phase– Next 12 hours of

calcification– 90% of Ca deposition– 180-200 mg Ca/hour

Eggshell Formation• ~5.5 g of eggshell per egg• ~2.2 g of Ca

• Eggshell composition– 95% CaCO3

– 0.3% P– 0.3% Mg

Eggshell Formation• Egg size increases with hen age (body weight)• Shell deposition remains constant

Issues in Shell Quality• 250 eggs = ~20 times total bone Ca reserves• After peak production, a consistent amount of

shell material is put on each egg– Larger eggs, thinner shells

Calcium Metabolism• Eggshell formation

– demand for Ca from ~6-24 hrs of ovulation cycle• enough skeletal calcium for ten

eggshells

• enough medullary bonefor one eggshell

ANSC 463

Calcium Metabolism• Eggshell formation

– 60-80% of calcium required for eggshell formation derived directly from the diet on shell-forming days

– the greater the proportion of eggshell calcium derived from bone stores, the poorer the shell quality

ANSC 463

Implications• Shell quality problems are often seen before

bone problems

17 22 24 26 28 30 3118 20

18 wks

20 wks

22 wks

24 wks

26 wks

Experimental Design

• 1.00 % Ca (grower)

3.25 % Ca (breeder)

5051525354555657

18 C 28 C

Egg

Wei

ght (

g)

a abbc c c

cdcc

dee

2018 22 24 26 2018 22 24 26

P<0.01

Average Egg Weight to 31 Weeks

0

1

2

3

4

5

6

18 C 28 C

Shel

l Wt (

g)

2018 22 24 26 2018 22 24 26

ab ab ab bbb c c c

P<0.0008

Shell Weight

1.075

1.078

1.080

1.083

1.085

18 C 28 C

Spec

ific

Grav

ity

2018 22 24 26 2018 22 24 26

P<0.0605

Specific Gravity

Broiler Breeders vs Layers• Time of switch to high Ca diet is important in

broiler breeders– Especially at high temperatures

• Laying hens seem to be less sensitive to early switch– Effect of high temperature?

Soluciones

Nutrients & Eggshell Formation• Ca level; Ca-P ratio

– Change with age• Vitamin D

– Reduced metabolism with hen age• NaCl – feed, water

– High NaCl reduces shell quality• Phytate

– Binds Ca, P

Nutrients & Eggshell Formation• Trace minerals

– Copper – lysyl oxidase• Cross-links in shell membrane fibers

– Manganese• Mucopolysaccharide formation – mammilary layer

– Zinc• Carbonic anhydrase – bicarbonate ion secretion

Management & Eggshell Formation • Body weight at placement

– Small pullets may lack sufficient medullary bone

• Pre-lay or not pre-lay?– Not before 10 days prior to first egg

• Switch to high Ca layer diet– ~5% production

Management & Eggshell Formation • Environmental temperature

– Minimize heat stress

• Electrolyte balance– Panting causes a loss of CO2

– Blood pH increases from 7.2 to 7.5-7.7• Loss of bicarbonate ions limits CaCO3

– Limits shell formation

Feed Intake• Feed particle size

– large particle calcium sources• 2/3 large particle (> 1mm)

– Retained in gizzard• 1/3 small particle (<1 mm)

– Quickly available

• Top-dress feed (emergency)

Eggshell Formation

Hendrix Genetics

Feed Intake• Brown layers

– Begin eggshell formation ~4 hours before lights out

– Encourage feed intake during the last 6 hours of the day

– Midnight feeding– Particle size

• 70% particles of 2-4 mm – slow release• 30% particles of <1 mm – quick release

Feed Intake• White layers

– Begin eggshell formation just before lights out– Encourage feed intake during the last 4 hours of

the day– Midnight feeding

• 50% particles of 2-4 mm – slow release• 50% particles of <1 mm – quick release

ANSC 463

Egg Production in Layersresponse to 1 hr of light @ 12 AM

Weeks of Production20 22 24 26 28 30 32 34 36 38

% H

en D

ay P

rodu

ction

0

10

80

90

100

***

**

*

SupplementalLighting

begun

Feed Supplements• Phytate• Vitamin C• Trace Minerals• Vitamin D3

– 25-OH Vitamin D3

Strain 0.0005Diet 0.0449S x D NS

Defective Shells

4.6

7.7

1.92.9

0123456789

W36-D W36-25-OH D3 W98-D W98-25-OH D3

Num

ber

of E

ggs p

er H

en

Bone Density

Strain NS Diet P=0.0386 S x D NS

105.8 95.8 107.3 95.4

0255075

100125

W36-D W36-25-OH D3 W98-D W98-25-OH D3

Bon

e M

iner

al D

ensi

ty (m

g/cm

3 ) 892.5 885.8916.2898.1

0200400600800

1000

W36-D W36-25-OH D3 W98-D W98-25-OH D3

Strain P=0.0296 Diet NS S x D NS

Cortical

Medullarya bb a

Heat Stress• Electrolyte balance

– Panting causes a loss of CO2

• Replace 30-35% of NaCl with NaHCO3

ANSC 463

• Possible solutions to low calcium status:– water supplementation of calcium

Calcium Metabolism

Conclusions• Shell quality problems can be caused by many

factors

• Shell quality problems often precede bone quality problems.

• Practical solutions can be used to prevent & correct problems

Muchas gracias